The invention relates to a bore resistance measuring apparatus comprising a drill attachment and a driving mechanism according to the preamble of claim 1, as it is known from DE-A-443 383.
In a method known as such (DE 35 018 41 C1) holes are drilled into objects which mainly consist of wood using a long needle-like drill wherein the penetration resistance is measured, recorded and/or electronically stored. From the resistance diagram determined in this way conclusions can be made concerning the inner structure of the test object for dendrochronological purposes, the determination of growth rates, the effects of diseases and the examination of load capacity.
The drills known so far which are operated by electric batteries include a drill motor which is movably supported on a sliding carriage which is movable along a slide track and where back-and-forward movement is effected by a drive motor via a screw or gear drive. Also, a drive arrangement has become known wherein the drive motor is also arranged on the slide carriage for the drill motor and moves itself by way of a pinion engaging a stationary spur rack. Before the long drill needle has entered the object to be examined up to a certain depth, the drill needle must be supported because otherwise it would form a vibration belly under the effect of the drill needle advancing force. Then tubes are used as support elements which move telescopically over one another as the drill needle is advanced.
Some apparatus models include recording devices in order to be able to control the drilling already while in progress. The plotting or recording devices may be arranged within the housing of the apparatus or at the outside thereof. Power is supplied from an external battery by way of a cable; but other apparatus are known wherein the battery is mounted to the housing of the drilling apparatus. Without exception, the known drilling apparatus include a tubular protective sleeve of angular or circular cross-section having a front end with an opening through which the drill needle extends and a rear end with a handle having switching, plug-and control elements and, within the tube, a guide track and the needle support elements.
The drill resistance measurement for tree and wood examinations has been widely used since it has become known. However, for a wider use, it is disadvantageous that the price for the examination equipment is relatively high; and the reason herefor, in turn, is that the equipment is needed in only small numbers so that it is not worthwhile to mass-produce the equipment.
The elements described which are needed for the method require of course a certain space in all three directions and also have a relatively high weight.
Since drill tests must be performed in many cases from locations which are difficult to access for example, among the branches of trees, at high ceilings in buildings while standing on ladders, or in attics which are difficult to access the equipment must often be held above the head and guided by hand. In the process, canting of the drill needle or a deviation from the direction of drilling must be avoided.
From DE-A-41 22 492, a drill resistance measurement apparatus is known with all these features wherein a planetary transmission cannot serve as a force receiver.
It is the object of the invention to provide a drill resistance measuring device with the smallest possible dimensions and the smallest possible weight which permits easy and safe handling and which can be manufactured at reasonably low costs.